Lamination structure and a method for manufacturing the same

ABSTRACT

Metal plates are placed on opposed surfaces of two heating plates, the metal plates are heated. Then, a hollow plate is placed between the two heating plates, and the two heating plates are moved toward each other. The metal plates, which are heated to a high temperature, are bonded to the outer surfaces of the hollow plate by thermal fusion caused by the heat of the metal plates. After the metal plates are brought into planar contact with the hollow plate, the heating plates are moved away from each other. The heating plates sandwich the hollow plate only for a very short time. Thus, the heat of the heating plates is not transferred excessively to the hollow plate.

CLAIM OF PRIORITY

This application is a divisional of and claims the benefit of priorityunder 35 U.S.C. § 120 to U.S. patent application Ser. No. 15/377,983,filed on Dec. 13, 2016, which claims the benefit of priority under 35U.S.C. § 119 to Japanese Patent Application No. 2016-088518, filed onApr. 26, 2016, and to Japanese Patent Application No. 2016-006297, filedon Jan. 15, 2016, and to Japanese Patent Application No. 2015-246653,filed on Dec. 17, 2015, each of which are incorporated by referenceherein in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a lamination structure including ahollow plate made of a thermoplastic resin and a metal plate bonded tothe hollow plate, and to a method for manufacturing the laminationstructure.

A conventional hollow plate is known that has a plurality of cells eachhaving the shape of a polygonal or cylindrical column. For example,Japanese Laid-Open Patent Publication No. 2010-247448 describes a hollowplate including a core layer in which a plurality of cells each havingthe shape of a hexagonal column is arranged. The core layer is formed byfolding a sheet member that is made of a thermoplastic resin and has apredetermined shape. A superficial layer, which is a sheet member madeof a thermoplastic resin, is bonded to each of the upper and lower sidesof the core layer. The hollow plate is planar as a whole.

Further, a lamination structure is known in which metal plates arebonded to the hollow plate described above to improve the strength andappearance. For example, Japanese Laid-Open Patent Publication No.10-156985 describes a composite plastic structure of high strength andrigidity that is manufactured by bonding a metal plate, which may bemade of steel, stainless, or aluminum, to one or both sides of a hollowplate, which is made of a thermoplastic resin. Such a laminationstructure may be manufactured by placing a metal plate on the uppersurface of the hollow plate and pressing the metal plate from above witha heated jig to thermally fuse the hollow plate to the metal plate.

In this method for thermally fusing the hollow plate to the metal plate,the heated jig heats the superficial layer of the hollow plate throughthe metal plate. This process requires time to heat the metal plate andthe superficial layer to adequate temperatures. Thus, when thesuperficial layer melts, the core layer of the hollow plate is alsoheated and melted. This softens the core layer in the middle section inthe thickness direction of the hollow plate, causing the cell structureof the hollow plate to be easily compressed by the pressing pressureduring thermal fusion. The strength of the lamination structure istherefore reduced.

SUMMARY OF THE INVENTION

It is an objective of the present invention to provide a laminationstructure that is less likely to form scratches or dents in an objectwhen the lamination structure strikes the object and a method formanufacturing a lamination structure that limits softening of the middlesection in the thickness direction of a hollow plate when a metal plateis bonded to the hollow plate by thermal fusion.

To achieve the foregoing objective and in accordance with a first aspectof the present invention, a method is provided for manufacturing alamination structure in which a metal plate is bonded, by thermalfusion, to a hollow plate that is made of a thermoplastic resin andincludes a plurality of cells formed inside the hollow plate. The methodincludes: heating the metal plate; and placing the heated metal plate ona surface of the hollow plate and bonding the metal plate to the hollowplate by thermal fusion caused by heat of the metal plate.

A hollow plate and a metal plate are laminated and trimmed to have adesired planar shape and used for various applications as a laminationstructure. The hollow plate and the metal plate may be flush with eachother in the edge of a trimmed lamination structure. When such an edgeof the lamination structure strikes an object, the edge of the metalplate, which has a relatively high strength, tends to apply impact forceto the object, forming scratches or dents in the object.

To achieve the foregoing objective and in accordance with a secondaspect of the present invention, a lamination structure is provided inwhich a metal plate is bonded to a hollow plate that is made of athermoplastic resin and includes a plurality of cells formed inside thehollow plate. The metal plate includes an edge located inward of an edgeof the hollow plate in a plane direction of the lamination structure.

Lamination structures are light yet strong. As such, laminationstructures have been used for vehicle parts, which need to be lighter toimprove fuel efficiency. Examples of such vehicle parts include planarparts, such as luggage boards and cargo covers. However, the complexplastic structure described in Japanese Laid-Open Patent Publication No.10-156985 is formed merely by bonding flat metal plates to a hollowplate made or a thermoplastic resin and thus not suitable for vehicleparts. This structure has limited usability.

To achieve the foregoing objective and in accordance with a third aspectof the present invention, a lamination structure is provided thatincludes a hollow plate that is made of a thermoplastic resin andincludes a plurality of cells formed inside the hollow plate and a metalcomponent that is bonded to the hollow plate. The hollow plate includesa plastic recess that is thermally deformed by the metal component. Themetal component is bonded to the plastic recess.

To achieve the foregoing objective and in accordance with a fourthaspect of the present invention, a lamination structure is provide thatincludes a hollow plate that is made of a thermoplastic resin andincludes a plurality of cells formed inside the hollow plate and metalplates that are bonded to opposite surfaces of the hollow plate. Atleast one of surfaces of the lamination structure to which the metalplates are bonded includes a recess formed by thermal deformation. Inthe recess, the cells of the hollow plate are thinned.

To achieve the foregoing objective and in accordance with a fifth aspectof the present invention, a method is provided for manufacturing alamination structure in which a metal plate is bonded, by thermalfusion, to a hollow plate that is made of a thermoplastic resin andincludes a plurality of cells formed inside the hollow plate. The methodincludes: stamping the metal plate to form a recess in the metal plate;heating the metal plate including the recess; and placing the heatedmetal plate on a surface of the hollow plate and bonding the metal plateto the hollow plate by thermal fusion caused by heat of the metal plate.

Other aspects and advantages of the present invention will becomeapparent from the following description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1A is a perspective view showing a lamination structure accordingto a first embodiment of the present invention;

FIG. 1B is a cross-sectional view taken along line 1B-1B in FIG. 1A;

FIG. 1C is a cross-sectional view taken along line 1C-1C in FIG. 1A;

FIG. 2A is a perspective view showing a sheet member for forming a corelayer of a hollow plate;

FIG. 2B is a perspective view showing a state where the sheet member isbeing fold;

FIG. 2C is a perspective view showing the sheet member in the foldedstate;

FIGS. 3A to 3I are explanatory diagrams showing a method for bondingmetal plates to a hollow plate;

FIG. 4A is a perspective view showing a lamination structure accordingto a second embodiment of the present invention;

FIG. 4B is a cross-sectional view taken along line 4B-4B in FIG. 4A;

FIG. 4C is a cross-sectional view taken along line 4C-4C in FIG. 4A;

FIG. 5A is an explanatory diagram showing a periphery sealing process;

FIG. 5B is a partially enlarged view of FIG. 5A;

FIGS. 6A to 6C are cross-sectional views showing a lamination structurein a periphery sealing process;

FIG. 7 is a cross-sectional view showing a lamination structure of amodification;

FIG. 8 is a cross-sectional view showing a lamination structure of amodification;

FIG. 9 is a perspective view showing a lamination structure according toa third embodiment of the present invention;

FIG. 10A is a partial perspective view showing an upper metal plate;

FIG. 10B is a partial perspective view showing a hollow plate;

FIGS. 11A and 11B are diagrams showing a method for forming a metalrecess in a metal plate;

FIG. 11C is a partial perspective view showing the metal plate includingthe metal recess;

FIG. 11D is a partial perspective view showing the back side of themetal plate including the metal recess;

FIGS. 12A to 12I are explanatory diagrams showing a method for bondingmetal plates to a hollow plate;

FIGS. 13A to 13C are cross-sectional views taken along line 13-13 inFIG. 9 each showing a state of a recess in a lamination structure;

FIGS. 14A and 14B are diagrams showing a method for stamping a metalplate according to a modification;

FIG. 15A is a partial perspective view showing a modification of arecess in a lamination structure;

FIG. 15B is a cross-sectional view showing another modification of arecess in a lamination structure;

FIG. 15C is a partial perspective view showing another modification of arecess in a lamination structure;

FIG. 15D is a cross-sectional view showing another modification of arecess in a lamination structure; and

FIGS. 16A to 16D are partial perspective views showing othermodifications of a recess in a lamination structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

Referring to FIGS. 1A to 3I, a first embodiment of a laminationstructure according to the present invention and a method formanufacturing the same will now be described.

As shown in FIG. 1A, the lamination structure includes a hollow plate10, which has the shape of a hollow plate as a whole, and metal plates50 and 60, which are placed on the upper and lower sides of the hollowplate 10. As shown in FIG. 1A, the hollow plate 10 includes a core layer20, in which cells S are arranged side by side, and sheet shapedsuperficial layers 30 and 40, which are bonded to the upper and lowersides of the core layer 20.

Referring to FIGS. 1B and 1C, the core layer 20 is formed by folding asingle sheet member, which is made of a thermoplastic resin and has apredetermined shape. The core layer 20 includes upper walls 21, lowerwalls 22, and side walls 23. The side walls 23 extend between the upperwalls 21 and the lower walls 22 and define cells S inside the core layer20. Each cell S has the shape of a hexagonal column.

The cells S include first cells S1 and second cells S2, which differ instructure from the first cells S1. Each first cell S1 has a double-layerupper wall 21 above the side walls 23. The layers of the upper wall 21are bonded to each other. In addition, the first cell S1 has asingle-layer lower wall 22 under the side walls 23. In contrast, eachsecond cell S2 has a single-layer upper wall 21 above the side walls 23.In addition, the second cell S2 has a double-layer lower wall 22 underthe side walls 23. The layers of the lower wall 22 are bonded to eachother. Adjacent first cells S1 are separated by double-layer side walls23, and adjacent second cells 82 are separated by double-layer sidewalls 23. Each double-layer side wall 23 includes a middle section inthe thickness direction of the core layer 20 where the layers are notthermally fused to each other. Accordingly, the internal cavity of eachcell communicates with the internal cavities of other cells S throughthe non-fused section in the side walls 23.

As shown in FIGS. 1A to 1C, the first cells S1 are arranged to form aline along the X-axis. Similarly, the second cells S2 are arranged toform a line along the X-axis. The lines of first cells S1 and secondcells S2 are arranged alternately along the Y-axis. The Y-axis isperpendicular to the X-axis. The core layer 20 as a whole has ahoneycomb structure of first and second cells S1 and S2.

A superficial layer 30, which is a sheet member made of a thermoplasticresin, is bonded to the upper surface of the core layer 20. In addition,a superficial layer 40, which is a sheet member made of a thermoplasticresin, is bonded to the lower surface of the core layer 20. The corelayer 20 and the superficial layers 30 and 40 form the hollow plate 10,which has the shape of a hollow plate. In FIGS. 1B and 1C, referencenumerals are given only to the leftmost cell S among the plurality ofcells S shown, but the other cells S have the same configurations.

A metal plate 50 is bonded to the upper surface of the hollow plate 10,which is an outer surface of the superficial layer 30, by thermalfusion. The metal plate 50 may be made of a metal, such as aluminumalloy, ferrous alloy, or copper alloy, and have a thickness of about0.05 to 4 mm, preferably of 2 mm or less, for example. A metal plate 60is bonded to the lower surface of the hollow plate 10, which is an outersurface of the superficial layer 40, by thermal fusion. The metal plate60 is identical to the metal plate 50 in structure.

Referring to FIGS. 2A to 3I, a method for manufacturing a laminationstructure according to a first embodiment will now be described. First,a method for manufacturing the hollow plate 10 will be described.

As shown in FIG. 2A, a first sheet member 100 is produced by forming asingle sheet, which is made of a thermoplastic resin, into apredetermined shape. The first sheet member 100 includes flat regions110 in a strip shape and protrusion regions 120, which alternate in thelongitudinal direction of the first sheet member 100 (the X-axis). Eachprotrusion region 120 also includes a first protrusion section 121,which extends over the entire length of the protrusion region 120 in thedirection in which the protrusion region 120 extends (the Y-axis). Thefirst protrusion section 121 has the shape of an inverted groove formedby an upper surface and two side surfaces. The upper surface of thefirst protrusion section 121 preferably form an angle of 90° with theside surfaces, and thus the cross-section of the first protrusionsection 121 has the shape of inverted letter U. The width of the firstprotrusion section 121, which is the transverse dimension of the uppersurface of the first protrusion section 121, is equal to the width ofthe flat regions 110. The width of the first protrusion section 121 isdouble the protrusion height of the first protrusion section 121, whichis the transverse dimension of the side surfaces of first protrusionsection 121.

Each protrusion region 120 includes second protrusion sections 122,which are perpendicular to the first protrusion section 121. Thecross-section of each second protrusion section 122 has the shape of atrapezoid that is obtained by dividing a regular hexagon into equalhalves by the longest diagonal line. The protrusion height of the secondprotrusion sections 122 is equal to the protrusion height of the firstprotrusion section 121. The distance between adjacent second protrusionsections 122 is equal to the width of the upper surfaces of the secondprotrusion sections 122.

The first and second protrusion sections 121 and 122 are formed bypartly deforming the sheet to protrude upward using the plasticity ofthe sheet. The first sheet member 100 is formed from a single sheetusing a known method, such as vacuum forming or compression forming.

As shown in FIGS. 2A and 2B, the core layer 20 is formed folding thefirst sheet member 100 along borderlines P and Q. Specifically, thefirst sheet member 100 is first folded to form a valley along each ofthe borderlines P between flat regions 110 and protrusion regions 120,and then folded to form a ridge alone each of the borderlines Q betweenthe upper surfaces and the side surfaces of the first protrusionsections 121 so that the first sheet member 100 is compressed along theX axis. As shown in FIGS. 2B and 2C, the upper surface of each firstprotrusion section 121 is folded over the side surfaces, and the endsurface of each second protrusion section 122 is folded over the flatregion 110. Thus, in the first sheet member 100, one protrusion region120 forms one partitioned element 130, which has the shape of a columnextending along the Y-axis. The partitioned elements 130 are formedcontinually along the X-axis, thereby forming the core layer 20 havingthe shape of a hollow plate.

When the first sheet member 100 is compressed, the upper surfaces andthe side surfaces of the first protrusion sections 121 form the upperwails 21 of the core layer 20, and the end surfaces of the secondprotrusion sections 122 and the flat regions 110 form the lower walls 22of the core layer 20. The upper walls 21 where the upper surfaces of thefirst protrusion sections 121 are folded over the side surfaces to formdouble-layer structure and the lower walls 22 where the end surfaces ofthe second protrusion sections 122 are folded over the flat regions 110to form double-layer structure serve as overlap sections 131.

The regions that are formed by the folded second protrusion sections 122and each have the shape of a hexagonal column serve as second cells S2,and the regions formed between corresponding two adjacent partitionedelements 130 and each have the shape of a hexagonal column serve asfirst cells S1. The upper surfaces and side surfaces of the secondprotrusion sections 122 form the side walls 23 of the second cells S2,and the side surfaces of the second protrusion sections 122 and the flatsections of the protrusion regions 120 between the second protrusionsections 122 form the side walls 23 of the first cells S1. The sectionswhere the upper surfaces of second protrusion sections 122 are incontact with each other and the sections where the flat sections of theprotrusion region 120 are in contact with each other separately formdouble-layer side walls 23. The first sheet member 100 is preferablyheated and softened before the folding process.

A second sheet member, which is made of a thermoplastic resin, is bondedto each of the upper and lower surfaces of the core layer 20 by thermalfusion. The second sheet member bonded to the upper surface of the corelayer 20 serves as the superficial layer 30, and the second sheet memberbonded to the lower surface of the core layer 20 serves as thesuperficial layer 40.

When thermally fusing the superficial layers 30 and 40 to the core layer20, the double-layer upper walls 21 (overlap sections 131) of the firstcells S1 are thermally fused, and similarly the double-layer lower walls22 (overlap sections 131) of the second cells S2 are thermally fused.The double-layer side walls 23 of the first and second cells S1 and S2receive less heat than the upper and lower walls 21 and 22. As a result,each double-layer side wail 23 includes a middle section in thethickness direction of the hollow plate 10 that is not bonded by thermalfusion. Accordingly, the internal cavities of cells S are not completelysealed and communicate with one another through gaps between thedouble-layer side walls 23 that are not bonded by thermal fusion.

Referring to FIGS. 3A to 3I, a method for manufacturing a laminationstructure by bonding metal plates 50 and 60 to a hollow plate 10 willnow be described.

As shown in FIG. 3A, first, a metal plate 50 is placed on one side inthe thickness direction (first surface) of a flat support plate 210, anda metal plate 60 is placed on the other side in the thickness direction(second surface) of the support plate 210. The first and second surfacesof the support plate 210 each include air suction holes. The first andsecond surfaces of the support plate 210 attract and support the metalplates 50 and 60 when air is drawn through the air suction holes in thesupport plate 210.

Then, as shown in FIG. 3B, the support plate 210, on which the metalplates 50 and 60 are supported, is placed between two heating plates220. The plane shape of the heating plates 220, which function asheating members, is larger than or equal to the plane shape of the metalplates 50 and 60. In FIGS. 3A to 3I, the heating plates 220 and themetal plates 50 and 60 are shown as the same size. The opposed surfacesof the heating plates 220 are heated to a temperature higher than orequal to the melting temperature of the thermoplastic resin forming thehollow plate 10, which may be several hundred degrees or higher, forexample. The opposed surfaces of the heating plates 220 each include airsuction holes. The opposed surfaces of the heating plates 220 attractand support the metal plates 50 and 60 when air is drawn through the airsuction holes in the heating plates 220.

After placing the support plate 210, on which the metal plates 50 and 60are supported, between the two heating plates 220, the two heatingplates 220 are moved toward each other as shown in FIG. 3C. As indicatedby the arrow in FIG. 3C, the two heating plates 220 sandwich the supportplate 210, on which the metal plates 50 and 60 are supported. In thisstate, at least one of the air suction through the support plate 210 andthe air suction through the heating plates 220 is performed. As such,the metal plates 50 and 60 are supported by the support plate 210 and/orthe heating plates 220 and thus held between the support plate 210 andthe heating plates 220. In this state, the entire surfaces of the metalplates 50 and 60 are in planar contact with the opposed surfaces of theheating plates 220 and therefore heated by the heat of the heatingplates 220. The step in which the heating plates 220 support the metalplates 50 and 60 corresponds to the heating step of heating the metalplates 50 and 60.

Then, as shown in FIG. 3D, the heating plates 220, on which the metalplates 50 and 60 are supported, are moved away from each other. Thesupport plate 210 is then moved in the direction of the arrow in FIG. 3Daway from between the two heating plates 220. After moving the supportplate 210, as shown in FIG. 3E, a hollow plate 10 is placed between thetwo heating plates 220. In this state, the metal plates 50 and 60, whichare in planar contact with the opposed surfaces of the two heatingplates 220, face the outer surfaces of the hollow plate 10.

After placing the hollow plate 10 between the two heating plates 220, asshown in FIG. 3F, the two heating plates 220 are moved toward eachother. This moves the heating plates 220 toward the hollow plate 10 andbrings the heated metal plates 50 and 60, which are supported byrespective heating plates 220, into planar contact with the outersurfaces of the hollow plate 10. Here, the metal plates 50 and 60, whichare heated to a high temperature, are bonded to the outer surfaces ofthe hollow plate 10 by thermal fusion caused by their own heat. Afterthe metal plates 50 and 60 are brought into planar contact with theouter surfaces of the hollow plate 10, the air suction through theheating plates 220 is stopped, and the heating plates 220 are moved awayfrom each other. In this process, the heating plates 220 sandwich thehollow plate 10 through the metal plates 50 and 60 only for a very shorttime. Thus, the heat of the heating plates 220 is not transferredexcessively to the hollow plate 10. The step described above, in whichthe hollow plate 10 is placed between the two heating plates 220 onwhich the metal plates 50 and 60 are supported, the metal plates 50 and60 are bonded to the outer surfaces of the hollow plate 10 by thermalfusion, and the heating plates 220 are moved away from each other,corresponds to the thermal fusion step.

After bonding the metal plates 50 and 60 to the outer surfaces of thehollow plate 10 by thermal fusion, as shown in FIG. 3G, the hollow plate10, which is placed between the two heating plates 220 is moved to beplaced between two press plates 230. The plane shape of the press plates230 is larger than or equal to the plane shape of the metal plates 50and 60. In FIGS. 3A to 3I, the press plates 230 and the metal plates 50and 60 are shown as the same size. Unlike the heating plates 220, thepress plates 230 are riot heated and have ordinary temperature. Afterplacing the hollow plate 10 between the two press plates 230, the pressplates 230 are moved toward each other. The two press plates 230sandwich and press the hollow plate 10 in the thickness direction with apredetermined pressure. The press plates 230 thus press the entire areasof the metal plates 50 and 60 against the hollow plate 10. As such, themetal plates 50 and 60 are pressed against and bonded to the hollowplate 10 under uniform pressure. This adjusts the thickness of thelamination structure and forms a flat planar lamination structure thatis free from warpage. Then, the two press plates 230 are moved away fromeach other. As shown in FIG. 3I, the hollow plate 10 to which the metalplates 50 and 60 are bonded by thermal fusion, or a laminationstructure, is then moved away from between the two press plates 230.

As described above, the heated metal plates 50 and 60 are bonded to thehollow plate 10 by thermal fusion caused by their own heat. Accordingly,the hollow plate 10 receives only a very small amount of heat from theheating plates 220. Further, the press plates 230 are not heated forthermal fusion. Thus, even if the metal plates 50 and 60 still maintaina high temperature when the press plates 230 press the hollow plate 10,the press plates 230 absorb heat from the metal plates 50 and 60 whilein contact with the metal plates 50 and 60. This rapidly cools the metalplates 50 and 60. As a result, heat is not transferred excessively tothe middle of the hollow plate 10 in the thickness direction, and themiddle section of the hollow plate 10 in the thickness direction is lesslikely to soften. Therefore, the structure of the cells S in the hollowplate 10 resists collapsing when the two press plates 230 press thehollow plate 10.

The first embodiment achieves the following advantages.

(1) The preheated metal plates 50 and 60 are brought into planar contactwith the outer surfaces of the hollow plate 10 and soften the outersurfaces of the hollow plate 10 with their own heat to achieve thermalfusion. With this method, the amount of heat that the hollow plate 10receives generally does not exceed the amount of heat retained in theheated metal plates 50 and 60. As a result, the hollow plate 10 does notreceive excessive heat from the metal plates 50 and 60, limitingsoftening of the middle section of the hollow plate 10 in the thicknessdirection.

(2) The heating plates 220 are moved away from each other immediatelyafter the metal plates 50 and 60 are brought into planar contact withthe outer surfaces of the hollow plate 10. Thus, the heating plates 220sandwich the hollow plate 10 through the metal plates 50 and 60 only fora very short time. This limits excessive transfer of heat from theheating plates 220 to the hollow plate 10.

(3) After the metal plates 50 and 60 are bonded to the outer surfaces ofthe hollow plate 10 by thermal fusion, the press plates 230 press thehollow plate 10. The metal plates 50 and 60 are thus pressed against andbonded to the hollow plate 10 under uniform pressure. This adjusts thethickness of the lamination structure and forms a flat planar laminationstructure that is free from warpage.

(4) The two press plates 230 are not heated for thermal fusion. Thus,even if the metal plates 50 and 60 maintain a high temperature afterbonded to the outer surfaces of the hollow plate 10 by thermal fusion,the two press plates 230 cool the metal plates 50 and 60. This limitsexcessive transfer of heat from the metal plates 50 and 60 to the hollowplate 10.

(5) The plane shape of the two heating plates 220 is larger than theplane shape of the metal plates 50 and 60, and the metal plates 50 and60 are brought into planar contact with the opposed surfaces of theheating plates 220 and heated. This achieves uniform heating of themetal plates 50 and 60. In addition, the planar contact between themetal plates 50 and 60, which are supported on the heating plates 220,and the outer surfaces of the hollow plate 10 allows the metal plates 50and 60 to be uniformly bonded to the outer surfaces of the hollow plate10 by thermal fusion.

(6) The internal cavities of the cells S in the core layer 20 are notcompletely closed and communicate with one another. Thus, when bondingthe metal plates 50 and 60 to the outer surfaces of the hollow plate 10,the expanded air resulting from heated internal cavities of cells S maybe discharged out of the hollow plate 10 through the internal cavitiesof other cells S. Thus, the structure of the cells S of the hollow plate10 is less likely to be deformed, for example, by air expansionpressure.

The first embodiment may be modified as follows.

The first embodiment forms the core layer 20, which is of a honeycombstructure, by folding and shaping a single first sheet member 100 suchthat hexagonal cells S are formed in the core layer 20. However, thepresent invention is not limited to this method. For example, sheetstrips may be bent separately and arranged at predetermined intervals toform side walls of cells. Superficial layers may then be placed on theupper and lower sides of the sheet strips to form the upper and lowerwalls of cells. Alternatively, a known forming method, such as vacuumforming or compression forming, may be used to form protrusions anddepressions in sheet strips to form a core layer 20, and superficiallayers may be placed on the upper and lower sides of the core layer 20.Further, as described in Japanese Patent No. 4368399, athree-dimensional structure including protrusions of trapezoidalcross-section may be folded successively to form a honeycomb structureas a core layer 20.

The first embodiment forms cells S, each having the shape of a hexagonalcolumn, inside the core layer 20. However, there is no limitation to theshape of the cells S, and the cells S may have the shape of a polygon,such as quadrangular column or octagonal column, or a cylinder, forexample. The cells S may be shaped as a truncated cone. The cells S mayhave different shapes. Further, cells do not have to be adjacent to oneanother, and there may be a gap between adjacent cells S.

The hollow plate 10 does not have to include columnar cells S. Forexample, the hollow plate 10 may be formed by bonding superficial layersto the upper and lower sides of a core layer having a predetermineduneven shape. Such a hollow plate is described in Japanese Laid-OpenPatent Publication No. 2014-205341, for example. Alternatively, thehollow plate 10 may be a corrugated plastic board that has aharmonica-shaped cross-section.

The superficial layers 30 and 40 may be bonded to the core layer 20 inany method and may be bonded by adhesion or ultrasonic welding.

The superficial layers 30 and 40 may be multilayered. For example, thesuperficial layer 30 or 40 may include an adhesion layer, which melts ata relatively low temperature, and a functional layer, which hasadditional characteristics such as flame retardancy. In this case,adhesion layers are preferably placed on the surfaces of the superficiallayers that are to be bonded to the core layer 20 and the metal plates50 and 60.

Additional layers may be placed between the metal plates 50 and 60 andthe hollow plate 10 or the superficial layers 30 and 40. For example, anonwoven fabric may be bonded to the upper surface of the hollow plate10 or the superficial layer 30, and the metal plate 50 may be bonded tothe upper surface of the nonwoven fabric. In this case, the nonwovenfabric serves as a layer forming the hollow plate 10. Further, anadditional layer (e.g., nonwoven fabric) may be bonded to the uppersurface of the metal plate 50 or 60.

One or both of the superficial layers 30 and 40 may be omitted. In thecore layer 20 of the first embodiment, the layers of the double-layerupper wall 21 of each first cell S1 are bonded to each other by thermalfusion, and the layers of the double-layer lower wall 22 of each secondcell S2 are bonded to each other by thermal fusion. This allows the corelayer 20 by itself to maintain its planar shape and thus serve as thehollow plate 10. When the superficial layers 30 and 40 are not bonded tothe upper and lower sides of the core layer 20, the upper section ofeach first cell S1 and the lower section of each second cell S2 in thecore layer 20 are not completely closed. Thus, when bonding the metalplates 50 and 60 to the core layer 20 (hollow plate) by thermal fusion,the air introduced between the core layer 20 and the metal plates 50 and60 flows into the internal cavities of the first and second cells S1 andS2. In the first embodiment, the layers of each double-layer side wall23 of the cells S are not bonded to each other, allowing communicationbetween internal cavities of the cells S. Thus, the air introduced intothe internal cavity of a cell S is discharged out of the core layer 20through the internal cavities of other cells S. As such, when one orboth of the superficial layers 30 and 40 are omitted or the core layer20 is used as the hollow plate by itself, deairing process is notrequired to remove the air introduced when bonding the metal plates 50and 60 to the core layer 20 by thermal fusion. This limits bulging orsinking of the bonded metal plates 50 and 60 that may otherwise becaused by the air in the hollow plate 10.

One of the metal plates 50 and 60 may be omitted. That is, the metalplate 50 or 60 may be bonded to only one side of the hollow plate 10 bythermal fusion. This still limits warpage of the hollow plate 10.

The plane shape of the metal plates 50 and 60 may be in any relationshipwith the plane shape of the hollow plate. For example, the bonded metalplate 50 or 60 may be smaller than the plane shape of the hollow plate10. When the metal plate 50 or 60 is bonded to a part of the outersurface of the hollow plate 10, the hollow plate 10 is heated only inthe part to which the metal plate 50 or 60 is bonded. This limits changein the plate thickness and reduction in surface smoothness of the hollowplate 10 that may be caused by bonding of the metal plate 50 or 60. Inparticular, when the metal plate 50 or 60 is bonded to an area that issmaller than or equal to one-half or one-third of the entire outersurface of the hollow plate 10, the part of the core layer 20 to whichthe metal plate 50 or 60 is not bonded remains unheated, reducing thepossibility of the structure of cells S collapsing. This limits strengthreduction of the hollow plate 10.

The metal plates 50 and 60 may include holes, for example. Further, aslong as the hollow plate 10 is planar, the hollow plate 10 may be curvedor bent. In this case, the metal plates 50 and 60 are curved or bent toconform to the shape of the hollow plate 10.

A single metal plate may be extended over and bonded to a plurality ofhollow plates. In this case, bonding of the metal plate integrates thehollow plates into one plate member.

Each of the metal plates 50 and 60 may include a metal layer, which ismade of a metal, and a plastic layer, which is made of a thermoplasticresin and placed on at least one side of the metal laver. In this case,the heating plates 220 may be in planar contact with the metal layers ofthe metal plates 50 and 60 when supporting the metal plates 50 and 60.In addition, the heating temperature of the opposed surfaces of theheating plates 220 may be set to soften the plastic layers of the metalplates 50 and 60. The plastic layers in the metal plates 50 and 60increase the bonding strength between the hollow plate 10 and the metalplates 50 and 60. Further, the plastic layers in the metal plates 50 and60 may be made of a resin material that melts at a lower temperaturethan the resin material forming the hollow plate 10. Adhesion layers maybe added to the metal plates 50 and 60 by bonding adhesive film to themetal layers, or plastic layers may be formed on the metal layersthrough surface treatment, such as primer treatment or anchoringtreatment. Alternatively, an adhesive may be applied to the hollow plate10 or the metal plates 50 and 60. Hot melt adhesives may be used forthis purpose.

The metal plates 50 and 60 may be supported and moved by a structureother than the support plate 210. For example, a clamp for holding theupper sections of the metal plates 50 and 60 or a magnet, for supportingthe metal plates 50 and 60 by magnetic force may be used. Alternatively,the metal plates 50 and 60 may include depressions or holes into whichpins are fitted to support the metal plates 50 and 60. Further, theheating plates 220 and the hollow plate 10 may be moved instead of themetal plates 50 and 60.

When the two heating plates 220 sandwich the support plate 210 on whichthe metal plates 50 and 60 are supported, air suction through thesupport plate 210 may be stopped, and air suction through the heatingplates 220 may be started. In this case, as soon as the two heatingplates 220 sandwich the support plate 210, the metal plates 50 and 60are moved from the support plate 210 to the heating plates 220.

The support plate 210 and the two heating plates 220 may have airsuction holes of any structure as long as the holes allow supporting ofthe metal plates 50 and 60. The air suction holes may have a smallerdiameter to reduce the possibility that the holes leave marks on themetal plates 50 and 60.

The means to heat the metal plates 50 and 60 may be a burner, oven, orIH heater, for example. In this case, the heated metal plates 50 and 60may be supported by the support plate 210 and moved into planar contactwith the outer surfaces of the hollow plate 10.

The heating of the heating plates 220 may be stopped when the metalplates 50 and 60 are heated to a predetermined temperature or higher.This further limits transfer or excessive heat from the two heatingplates 220 to the hollow plate 10 through the metal plates 50 and 60.

The two press plates 230 may be cooed so as not to exceed apredetermined temperature. Cooling of the press plates 230 prevents thepress plates 230 from being heated to a high temperature even whenrepeatedly heated by the metal plates 50 and 60 during continuousmanufacturing of lamination structures.

As long as sufficient bonding strength and the flatness of the surfacesof the metal plates 50 and 60 are maintained, the step of sandwichingand pressing with the two press plates 230 may be omitted. Depending onthe bonding strength and appearance required for the laminationstructure, the pressing step may be performed or omitted.

FIGS. 3A to 3I show the components including the support plate 210 andthe heating plates 220 extending in the vertical direction. However,these components may be in any arrangement. For example, the componentsmay extend in the horizontal direction.

Second Embodiment

Referring to FIGS. 4A to 6C, a second embodiment of a laminationstructure and a method for manufacturing the same according to thepresent invention will now be described. The components of the secondembodiment that are the same as the corresponding components of thefirst embodiment will not be described in detail.

As shown in FIGS. 4A to 4C, the periphery of a hollow plate 310 includesa sealing section 311 that seals the hollow plate 310 so that theinternal cavities of the cells S are not exposed to the outside. Thesealing section 311 is formed by heating and compressing the peripheryof the hollow plate 310 inward. As such, the sealing section 311 isformed integrally with the hollow plate 310 from the thermoplastic resinforming the core layer 320 and the superficial layers 330 and 340 of thehollow plate 310. The sealing section 311 is formed over the entirecircumference of the hollow plate 310.

The sealing section 311 has a tetragonal cross-section as a whole. Morespecifically, the sealing section 311 includes upper and lower flatsurfaces 311 b, which extend in the plane direction of the laminationstructure (the lateral direction as viewed in FIGS. 4B and 4C), andupper and lower inclined surfaces 311 c, which obliquely extend in anarc shape from the respective flat surfaces 311 b toward the middle inthe thickness direction. The sealing section 311 also includes an endsurface 311 a, which extends between the inclined surfaces 311 c in thethickness direction of the lamination structure. The end surface 311 aof the sealing section 311 forms the edge of the hollow plate 310.Cavities S3, which are formed from internal cavities of cells S when thehollow plate 310 is compressed, are defined in the sealing section 311.FIGS. 4B and 4C show a cavity S3 in the sealing section 311 as having asemi-circular cross-section. However, the shape and size of each cavityS3 may vary depending on the temperature or compression degree in theformation of the sealing section 311. Further, FIGS. 4B and 4C show thesealing section 311 as a member separate from the core layer 320 and thesuperficial layers 330 and 340. However, the sealing section 311 isformed integrally with the core layer 320 and the superficial layers 330and 340.

The edge 350 a of the metal plate 350 is located inward of the edge ofthe hollow plate 310, which is the end surface 311 a of the sealingsection 311, in the plane direction of the lamination structure (locatedon the left side as viewed in FIGS. 4B and 4C). In other words, thesealing section 311 is located outward of the edge 350 a of the metalplate 350 in the hollow plate 310. The edge 360 a of the metal plate 360is located inward of the end surface 311 a of the sealing section 311 inthe plane direction of the lamination structure.

Referring to FIGS. 5A to 6C, a method for forming a sealing section 311in the periphery of a hollow plate 310, which is rectangular as viewedfrom above, will now be described.

First, in preparation for forming a sealing section 311 in the peripheryof a hollow plate 310, a metal plate 350 is bonded to the upper surfaceof the hollow plate 310 by thermal fusion. As shown in FIG. 5A, themetal plate 350 is bonded to the upper surface of the hollow plate 310such that the edge 350 a of the metal plate 350 is located inward of theedge of the hollow plate 310 in the plane direction of the hollow plate310. At this point, the periphery of the hollow plate 310 is not formedas a sealing section 311, and the hollow plate 310 does not include asealing section 311. As such, the edge of the hollow plate 310 is theedges of the core layer 320 and the superficial layers 330 and 340. Thedistance between the edge 350 a of the metal plate 350 and the edge ofthe hollow plate 310 is long enough to form the sealing section 311 andmay be 1 mm to 5 cm, preferably 3 to 10 mm. In addition, a metal plate360 is bonded to the lower surface of the hollow plate 310.

After bonding the metal plates 350 and 360 to the hollow plate 310, anotch 312 is formed in each of the four corners of the hollow plate 310.As shown in FIG. 5B, each notch 312 is square as viewed from above. Thevertical and lateral dimensions of the notch 312 are set such that thenotch 312 does not reach the metal plates 350 and 360 as viewed fromabove.

As shown in FIG. 5A, after the preparation process, the hollow plate 310is subjected to a periphery sealing process, which uses a pair ofshort-side sealing jigs 380 and a pair of long-side sealing jigs 390.The pair of short-side sealing jigs 380 and the pair of long-sidesealing jigs 390 are configured to be heated by an electromagneticheater, for example, to a temperature that is higher than the meltingtemperature of the thermoplastic resin forming the hollow plate 310.

Each short-side sealing jig 380 is an elongated member as a whole. Thelongitudinal dimension of the inner side of the short-side sealing jig380 is shorter than the longitudinal dimension of the outer side of theshort-side sealing jig 380. Accordingly, each end of the short-sidesealing jig 380 includes an inclined section 380 a. The inclined section380 a is at an angle of 45° to the longitudinal axis of the short-sidesealing jig 380. The longitudinal dimension of the inner side of theshort-side sealing jig 380 is slightly shorter than the length of theshort sides of the hollow plate 310, and the longitudinal dimension ofthe outer side of the short-side sealing jig 380 is slightly longer thanthe length of the short sides of the hollow plate 310.

As shown in FIGS. 6A to 6C, the inner side of the short-side sealing jig380 (the left side as viewed in FIGS. 6A to 6C) includes a groove 381,which extends outward (rightward as viewed in FIGS. 6A to 6C) and in thelongitudinal direction of the short-side sealing jig 380. The groove 381includes a base surface 382 and upper and lower inner surfaces 383 and384 extending perpendicular to the base surface 382. In addition, thegroove 381 includes an upper curved surface 383 a, which is arched andconnects the base surface 382 to the upper inner surface 383, and alower curved surface 384 a, which is arched and connects the basesurface 382 to the lower inner surface 384. The distance between theupper inner surface 383 and the lower inner surface 384 is slightlygreater than the thickness of the lamination structure, in which themetal plates 350 and 360 are bonded to the hollow plate 310 (thethickness between the upper surface of the metal plate 350 and the lowersurface of the metal plate 360). The groove 381 also includes an uppertapered surface 385, which is continuous with the upper inner surface383, and a lower tapered surface 386, which is continuous with the lowerinner surface 384. The distance between the upper tapered surface 385and the lower tapered surface 386 increases toward the opening of thegroove 381. That is, the distance between the upper tapered surface 385and the lower tapered surface 386 is greater than the thickness of thelamination structure, in which the metal plates 350 and 360 are bondedto the hollow plate 310.

As shown in FIG. 5A, each long-side sealing jig 390 is an elongatedmember as a whole. The longitudinal dimension of the inner side of thelong-side sealing jig 390 is shorter than the longitudinal dimension ofthe outer side of the long-side sealing jig 390. Accordingly, each endof the long-side sealing jig 390 includes an inclined section 390 a. Theinclined section 390 a is at an angle of 45° to the longitudinal axis ofthe long-side sealing jig 390. The longitudinal dimension of the innerside of the long-side sealing jig 390 is slightly shorter than thelength of the long sides of the hollow plate 310, and the longitudinaldimension of the outer side of the long-side sealing jig 390 is slightlylonger than the length of the long sides of the hollow plate 310. Theinner side of the long-side sealing jig 390 includes a groove 391, whichextends outward and in the longitudinal direction of the long-sidesealing jig 390. The groove 391 of the long-side sealing jig 390 isidentical in shape to the groove 381 of the short-side sealing jig 380.

As shown in FIG. 6A, when forming a sealing section 311 in the peripheryof a short side of the hollow plate 310, a heated short-side sealing jig380 is placed beside the periphery of the short side of the hollow plate310. Then, as shown in FIG. 6B, the base surface 382 of the groove 381in the short-side sealing jig 380 is pressed against the peripheral edgeof the short side of the hollow plate 310. Then, the edges of thesuperficial layers 330 and 340 of the hollow plate 310 are guided by theupper curved surface 383 a and the lower curved surface 384 a of thegroove 381 and bent toward the middle in the thickness direction of thehollow plate 310. As shown in FIG. 6C, when the base surface 382 of thegroove 381 in the short-side sealing jig 380 is further pressed againstthe hollow plate 310, the periphery of the short side of the hollowplate 310 is compressed toward the middle in the plane direction of thehollow plate 310. This forms a sealing section 311 in the periphery ofthe hollow plate 310.

As described above, the short-side sealing jig 380 is heated. Thus, thesection of the hollow plate 310 that is brought into contact with theshort-side sealing jig 380 melts and gains fluidity. Part of the meltedhollow plate 310 moves along the base surface 382, the upper curvedsurface 383 a, the lower curved surface 384 a, the upper inner surface383, and the lower inner surface 384 of the groove 381 and then hardens.As such, the outer shape of the sealing section 311 in the periphery ofthe short side of the hollow plate 310 is substantially identical to theinner shape of the groove 381 of the short-side sealing jig 380. Asshown in FIG. 4C, the sealing section 311 therefore includes a pair ofupper and lower flat surfaces 311 b and a pair of upper and lowerinclined surfaces 311 c.

The process of forming the sealing section 311 in the periphery of thehollow plate 310 as described above breaks the structure of some cells Sin the hollow plate 310. However, the internal cavities of the cells Sare unlikely to be completely filled with the molten resin. The cavities83 are thus formed in the sealing section 311. FIG. 6C shows a cavity S3having a semi-circular cross-section. However, the shape and size ofeach cavity S3 may vary depending on various conditions in the peripherysealing process.

As shown in FIG. 5A, the sealing section 311 is formed on the four sidesof the periphery of the hollow plate 310 simultaneously using the pairof short-side sealing jigs 380 and the pair of long-side sealing jigs390. Each short-side sealing jig 380 has an inclined section 380 a ineach end, and each long-side sealing jig 390 includes an inclinedsection 390 a in each end. Thus, when the short-side sealing jigs 380and the long-side sealing jigs 390 press the periphery of the hollowplate 310 simultaneously, the ends of the sealing jigs do not interferewith each other. In addition, the planar contact between the inclinedsections 380 a of the short-side sealing jigs 380 and the inclinedsections 390 a of the long-side sealing jigs 390 limits further inwardmovements of the short-side sealing jigs 380 and the long-side sealingjigs 390 in the plane direction of the hollow plate 310.

When the short-side sealing jigs 380 and the long-side sealing jigs 390press the periphery of the hollow plate 310, part of the melted hollowplate 310 is pressed toward the longitudinal ends of the jigs 380 and390 along the grooves 381 and 391 of the jigs 380 and 390. As such, themolten resin tends to flow to the border sections between the short-sidesealing jigs 380 and the long-side sealing jigs 390, which are the fourcorners of the hollow plate 310. If an excessive amount of resin flowsinto these sections, the resin tends to be squeezed out through the gapsbetween the inclined sections 380 a of the short-side sealing jigs 380and the inclined sections 390 a of the long-side sealing jigs 390 andharden, resulting in formation of fins. In this respect, as shown inFIG. 5B, the hollow plate 310 includes a notch 312 in each of the fourcorners. These notches 312 reduce the amount of plastic in the fourcorners of the hollow plate 310. Accordingly, the resin that flows intothe four corners of the hollow plate 310 is less likely to be squeezedout of the short-side sealing jigs 380 and the long-side sealing jigs390, reducing the possibility of fin formation.

The second embodiment achieves the following advantages.

(7) The edges 350 a and 360 a of the metal plates 350 and 360 arelocated inward of the end surface 311 a of the sealing section 311,which forms the edge of the hollow plate 310. Thus, when the end surface311 a of the sealing section 311 strikes an object, the edges 350 a and360 a of the metal plates 350 and 360, which are of relatively highstrength, are less likely to apply striking force to the object. Thisreduces the possibility of scratches or dents formed in the object thatis struck by the hollow plate 310.

(8) The sealing section 311 of the hollow plate 310 includes theinclined surfaces 311 c, which are inclined toward the middle in thethickness direction of the hollow plate 310, such that the end surface311 a is free from sharp corners. Thus, when the edge of the hollowplate 310 strikes an object, scratches or dents are less likely to beformed in the object. Absence of sharp corners in the end surface 311 aof the sealing section 311 of the hollow plate 310 limits ripping of acovering material covering the lamination structure that may otherwiseoccur from the section of contact between the covering material and acorner of the hollow plate 310. The covering material may be a fabric,nonwoven fabric, or vinyl-chloride sheet, for example.

(9) The periphery of the hollow plate 310 includes the sealing section311. The sealing section 311, which is formed by compressing theperiphery of the hollow plate 310, has a higher rigidity than thesection in which the sealing section 311 is not formed. Accordingly, theoverall rigidity of the lamination structure is improved compared to astructure that does not include the sealing section 311.

(10) The sealing section 311 is formed by heating and compressing theperiphery of the hollow plate 310. Thus, the sealing section 311 isformed integrally with the core layer 320 and the superficial layers 330and 340 of the hollow plate 310. Accordingly, the sealing section 311resists peeling and dropping from the hollow plate 310 compared to astructure in which the hollow plate 310 is sealed by bonding a separatemember to the peripheral edge of the hollow plate 310.

(11) The sealing section 311 is formed simultaneously on the four sidesof the hollow plate 310, which is rectangular as viewed from above. Thisreduces the time required to form the sealing section 311 compared to astructure in which the sealing section 311 is formed separately on thedifferent sides.

(12) A notch 312 is formed in each of the four corners of the hollowplate 310, which is rectangular as viewed from above, before forming thesealing section 311. Thus, even if an excessive amount of molten resinflows into the four corners of the hollow plate 310 when forming thesealing section 311 simultaneously on the four sides of the hollow plate310, the molten resin is less likely to be squeezed out of the sealingjigs and form fins.

The second embodiment may be modified as follows.

The sealing section 311 may be formed only in a part of thecircumference of the hollow plate 310. For example, the sealing section311 may be formed only on one side or opposite two sides of the foursides of the periphery of the hollow plate 310. Further, instead offorming the sealing section 311 over the entire area of each side of theperiphery of the hollow plate 310, the sealing section 311 may be formedonly in a part of each side.

Depending on the degrees of heating of the sealing jigs and thecompression of the periphery of the hollow plate 310 in the formation ofthe sealing section 311, there may be a case where cavities S3 are notformed in the sealing section 311.

During the periphery sealing process of the hollow plate 310, a moltenresin pool may be formed in a region between the metal plates 350 and360, for example between the edge 350 a of the metal plate 350 and theedge 360 a of the metal plate 360. The resin pool, after solidified,supports the metal plates 350 and 360 from the middle in the thicknessdirection of the hollow plate 310, thereby improving the overall impactstrength of the lamination structure. Such a resin pool is formed whenthe molten resin adheres to side walls 323 of the core layer 320.

The sealing section 311 of the hollow plate 310 may be omitted. In thiscase, the edge of the core layer 320 and the edges of the superficiallayers 330 and 340 form the edge of the hollow plate 310. As long as theedges 350 a and 360 a of the metal plates 350 and 360 are located inwardof the edges of the core layer 320 and the superficial layers 330 and340 in the plane direction of the hollow plate 310, any contact betweenthe metal plate 350 or 360, which is relatively strong, and an object isless likely to leave scratches in the object.

The sealing section 311 of the hollow plate 310 may be formed bysandwiching and compressing the periphery of the hollow plate 310 with apair of press plates from opposite sides in the thickness direction. Inthis case, the sealing section 311 is thinner than the core layer 320 ofthe hollow plate 310. Any structure may be employed as long as theinternal cavities of the cells S in the core layer 320 are not exposedto the outside.

The cross-sectional shape of the sealing section 311 may be modified asneeded. For example, when the groove 381 of each short-side sealing jig380 has an arcuate cross-section, the sealing section 311 will also havean arcuate cross-section. The same applies to the long-side sealing jigs390. In this case, the hollow plate 310 (sealing section 311) does notinclude the flat surfaces 311 b, and the arcuate surfaces function asthe inclined surfaces 311 c. In other embodiments, the hollow plate 310(sealing section 311) does not include the flat surfaces 311 b and onlyincludes the inclined surfaces 311 c. Further, one or both of the twoinclined surfaces 311 c of the sealing section 311 may be omitted. Inthis case, the flat surfaces 311 b of the sealing section 311 are at anangle of about 90° to the end surface 311 a.

The plane shape of the hollow plate 310 may be a polygonal shape otherthan rectangular shape, a circular shape, or a shape in which curves andstraight lines are combined if the hollow plate 310 has an arcuate edge,sealing jigs may be used that are arcuate conforming to the shape of theedge of the hollow plate 310.

Depending on various conditions in the periphery sealing process, theinner edge section of the sealing section 311 may cover the edges 350 aand 360 a of the metal plates 350 and 360. For example, referring toFIG. 6C, if the sealing section 311 is formed with part of molten resinspreading into between the upper tapered surface 385 and the metal plate350, the inner edge of the sealing section 311 protrudes over the metalplate 350 and covers the edge 350 a of the metal plate 350. The sameapplies to the metal plate 360.

The periphery sealing process of the hollow plate 310 does not have tobe performed simultaneously on the four sides of the hollow plate 310.For example, the sealing section 311 may first be formed on the twoshort sides of the hollow plate 310 and then formed on the two longsides. In this case, the short-side sealing jigs 380 do not interferewith the long-side sealing jigs 390. This allows the inclined sections380 a of the short-side sealing jigs 380 and the inclined sections 390 aof the long-side sealing jigs 390 to be omitted.

One sealing jig is used for each of the four sides of the hollow plate310 to form the sealing section 311. However, the present invention isnot limited to this structure. For example, a first sealing jig, whichextends along the entire length of a short side and a part of a longside of the hollow plate 310, and a second sealing jig, which extendsalong the entire length of a long side and a part of a short side of thehollow plate 310, may be used to perform the formation process of thesealing section 311 multiple times at the four corners of the hollowplate 310. This neatly forms a sealing section 311 at the four cornersof the hollow plate 310.

The notches 312 of the hollow plate 310 may be omitted. For example, ifthe degree of compression is reduced when compressing the periphery ofthe hollow plate 310 to form the sealing section 311, the amount ofmolten resin flowing into the four corners of the hollow plate 310 willbe moderate. In this case, formation of fins or the like is alreadylimited without forming the notches 312.

The sealing section 311 may be formed in the hollow plate 310 beforebonding the metal plates 350 and 360 to the hollow plate 310.

The flat surfaces or inclined surfaces may be formed in the hollow plate310 that does not include the sealing section 311. For example, in themodification shown in FIG. 7, a hollow plate 410 includes a flat surface410 b and an inclined surface 410 c located outward of the edge 450 a ofa metal plate 450. The flat surface 410 b is formed to have apredetermined width W from the edge 450 a of the metal plate 150. Theinclined surface 410 c is located in the edge section outward of theflat surface 410 b in the plane direction of the lamination structure.The inclined surface 410 c extends in an arc shape toward the middlesection in the thickness direction of the hollow plate 410. The upperinclined surface 410 c is formed by curving the edge sections of thesuperficial layer 430 and upper wails 421 of the core layer 420downward. Similarly, a flat surface 410 b and an inclined surface 410 care formed on the lower side of the hollow plate 410. The edge sectionin the circumference of the hollow plate 410 may be curved by pressingthe edge section against the groove 381 of the short-side sealing jig380 shown in FIGS. 6A to 6C, for example. In this case, the edges of thesuperficial layers 430 and 440 form the edge 410 a of the hollow plate410.

In the modification shown in FIG. 8, an upper flat surface 510 b has apredetermined width W from an edge 550 a of a metal plate 550 in thesimilar manner as the modification in FIG. 7. An inclined surface 510 cis located in the edge section outward of the flat surface 510 b in theplane direction of the lamination structure. The inclined surface 510 cextends linearly toward the middle section in the thickness direction ofthe hollow plate 510. The inclined surface 510 c is tapered such thatthe thickness of the hollow plate 510 decreases outward. Similarly, aflat surface 510 b and an inclined surface 510 c are formed on the lowerside of the hollow plate 510. The hollow plate 510 may be tapered bymachining the hollow plate 510 or by pressing the hollow plate 510 witha hot plate to partly melt the hollow plate 510, for example. In thiscase, the edge of the core layer 520 forms the edge 510 a of the hollowplate 510.

In the modifications shown in FIGS. 7 and 8, the section of the hollowplate 410, 510 that is located outward of the metal plates 450, 550 and460, 560 and thus not covered by the metal plates 450, 550 and 460, 560has a relatively low strength. Thus, to maintain the strength of thelamination structure, it is preferable that the section of the hollowplate 410, 510 that is located outward of the metal plates 450, 550 and460, 560 be narrower. However, when the section of the hollow plate 410,510 outward of the metal plates 450, 550 and 460, 560 is excessivelynarrow, the edges 450 a, 550 a and 460 a, 560 a of the metal plates 450,550 and 460, 560 are located near the edge 410 a, 510 a of the hollowplate 410, 510. To reduce impact applied to an object by the edges 450a, 550 a and 460 a, 560 a of the metal plates 450, 550 and 460, 560, itis preferable that the section of the hollow plate 410, 510 outward ofthe metal plates 450, 550 and 460, 560 be wider in view of the above,the width of the section of the hollow plate 410, 510 outward of themetal plates 450, 550 and 460, 560 is preferably 80% to 150% of thethickness of the plastic structure, and the width W of the flat surface410 b, 510 b is preferably less than or equal to the thickness of theplastic structure.

In the modifications shown in FIGS. 7 and 8, when the inclined surfaces410 c, 510 c of the hollow plate 410, 510 are formed by pressing aheated jig, part of molten resin may protrude over or cover the edges450 a, 550 a and 460 a, 560 a of the metal plates 450, 550 and 460, 560.

The lamination structure may be used for any applications, such as aplate for containers or cases for distribution/transportation or a platefor constructions, scaffolding, furniture like shelves or tables,vehicle cargo cover, or vehicle luggage board, for example. Further, thelamination structure may be used as a core material, and a coveringmaterial may be placed over the outer surface of the laminationstructure.

Third Embodiment

Referring to FIGS. 9 to 13C, a third embodiment of a laminationstructure and a method for manufacturing the same according to thepresent invention will now be described. The components of the thirdembodiment that are the same as the corresponding components of theforegoing embodiments will not be described in detail.

As shown in FIG. 9, the upper surface of a lamination structure, thatis, the upper surface of an upper metal plate 650, includes a recess670. The recess 670 is rectangular as viewed from above. The recess 670includes four side walls 671, which extend downward from a surface 652of the upper metal plate 650, and a rectangular base wall 672, which issurrounded by the side walls 671. The side walls 671 are substantiallyat a right angle to the surface 652 of the upper metal plate 650, andthe base wall 672 is substantially at a right angle to the side walls671.

As shown in FIG. 10A, the upper metal plate 650 includes a metal recess651. The metal recess 651 includes four side walls 655, which extenddownward from the upper surface 652 of the upper metal plate 650, and arectangular base wall 656, which is surrounded by the side walls 655.The upper metal plate 650 is a thin plate having a thickness of 0.05 mmto several mm. A metal protrusion 654, which corresponds to the metalrecess 651, protrudes downward from the lower surface 653 of the uppermetal plate 650.

As shown in FIG. 10B, a hollow plate 610 includes a plastic recess 611,where the hollow plate 610 is thermally deformed to be thinner. Theplastic recess 611 includes four side walls 612, which extend downwardfrom the surface of a superficial layer 630, and a rectangular base wall613, which is surrounded by the side walls 612. The section of thehollow plate 610 located under the base wall 613 has a thickness of 2 to15 mm. The thickness of this section is preferably less than or equal toone-half or one-third of the overall thickness of the hollow plate 610.

The back side of the metal recess 651 of the upper metal plate 650 isbonded to the plastic recess 611 of the hollow plate 610. That is, thesurface of the metal protrusion 654 of the upper metal plate 650 isbonded to the plastic recess 611 of the hollow plate 610. Specifically,the side walls 655 of the metal recess 651 (metal protrusion 654) arebonded to the side walls 612 of the plastic recess 611, and the basewall 656 of the metal recess 651 (metal protrusion 654) is bonded to thebase wall 613 of the plastic recess 611. The plastic recess 611 of thehollow plate 610 and the metal recess 651 of the upper metal late 650form the recess 670 of the lamination structure.

Referring to FIGS. 11A to 12I, a method for manufacturing a laminationstructure according to the third embodiment will now be described. Themethod for manufacturing the hollow plate 610 is the same as that of thefirst embodiment and will not be described in detail. A method formanufacturing a lamination structure having a recess 670 by bondingmetal plates 650 and 660 to the upper and lower sides of a hollow plate610 will now be described.

As shown in FIGS. 11A and 11B, an upper metal plate 650 is first stampedto form a metal recess 651. The upper metal plate 650 is placed on alower die 681 such that a surface 653 faces downward. The lower die 681includes a recess 681 a having the same shape as the metal recess 651.Then, an upper die 682, which includes a protrusion 682 a having thesame shape as the metal recess 651, is moved toward the lower die 681.This forms the metal recess 651 in a surface 652 of the upper metalplate 650 as shown in FIG. 11C. In addition, a metal protrusion 654,which has the same shape as the metal recess 651, is formed in thesurface 653 of the upper metal plate 650 as shown in FIG. 11D. The metalrecess 651 and the metal protrusion 654 are formed by stamping the thinupper metal plate 650 and thus form opposite sides of one section.

Then, as shown in FIG. 12A, the stamped upper metal plate 650 is placedon one side in the thickness direction (first surface) of a flat supportplate 6210, and a lower metal plate 660 is placed on the other side inthe thickness direction (second surface) of the support plate 6210.Here, the surface 653 of the upper metal plate 650 from which the metalprotrusion 654 protrudes faces toward the lower metal plate 660. Thesupport plate 6210 includes a recess, which is slightly larger than themetal protrusion 654, in the position corresponding to the metalprotrusion 654 of the upper metal plate 650. The recess of the supportplate 6210 receives the metal protrusion 654 of the upper metal plate650. Thus, the metal protrusion 654 of the upper metal plate 650 doesnot interfere with the support plate 6210 when placed on the firstsurface of the support plate 6210, and the surface 653 of the uppermetal plate 650 is in planar contact with the entire first surface ofthe support plate 6210. FIG. 12A shows the surface 652 of the uppermetal plate 650. Thus, the metal recess 651 of the upper metal plate 650is shown in FIG. 12A.

The first and second surfaces of the support plate 6210 each include aplurality of air suction holes. The first and second surfaces of thesupport plate 6210 attract and support the metal plates 650 and 660 whenair is drawn through the air suction holes in the support plate 6210.

Then, as shown in FIG. 12B, the support plate 6210, on which the metalplates 650 and 660 are supported, is placed between two heating plates6220 and 6230. The heating plate 6220, which faces the upper metal plate650, includes a protrusion 6221 in the position corresponding to themetal recess 651 in the surface 652 of the upper metal plate 650. Theprotrusion 6221 extends towards the upper metal plate 650 and has ashape that conforms to the inner shape of the metal recess 651. Theplane shape of the heating plates 6220 and 6230, which function asheating members, is larger than or equal to the plane shape of the metalplates 650 and 660. In FIGS. 12A to 12I, the heating plates 6220 and6230 and the metal plates 650 and 660 are shown as the same size.

The opposed surfaces of the heating plates 6220 and 6230 are heated to atemperature that is higher than or equal to the melting temperature ofthe thermoplastic resin forming a hollow plate 610. The opposed surfacesof the heating plates 6220 and 6230 include a plurality of air suctionholes. The opposed surfaces of the heating plates 6220 and 6230 attractand support the metal plates 650 and 660 when air is drawn through theair suction holes in the heating plates 6220 and 6230.

After placing the support plate 6210, on which the metal plates 650 and660 are supported, between the two heating plates 6220 and 6230, the twoheating plates 6220 and 6230 are moved toward each other as shown inFIG. 12C. As indicated by the arrow in FIG. 12C, the two heating plates6220 and 6230 sandwich the support plate 6210 on which the upper andlower metal plates 650 and 660 are supported. In this state, the entiresurfaces of the metal plates 650 and 660 are in planar contact with theopposed surfaces of the heating plates 6220 and 6230 and thereforeheated by the heat of the heating plates 6220 and 6230. In addition, theprotrusion 6221 of the heating plate 6220 facing the upper metal plate650 is placed in the metal recess 651 of the upper metal plate 650 sothat the outer surface of the protrusion 6221 is in contact with theinner surface defining the metal recess 651. As such, the metal recess651 (metal protrusion 654) of the upper metal plate 650 is heated by theheat of the protrusion 6221 of the heating plate 6220.

In this state, at least one of the air suction through the support plate6210 and the air suction through the heating plates 6220 and 6230 isperformed. Thus, the metal plates 650 and 660 are supported by thesupport plate 6210 and/or the heating plates 6220 and 6230 and thus heldbetween the support plate 6210 and the heating plates 6220 and 6230.

Then, as shown in FIG. 12D, the heating plates 6220 and 6230, on whichthe metal plates 650 and 660 are supported, are moved away from eachother. The support plate 6210 is then moved in the direction of thearrow in FIG. 12D away from between the two heating plates 6220 and6230. After moving the support plate 6210, the hollow plate 610 isplaced between the two heating plates 6220 and 6230 as shown in FIG.12E. In this state, the metal plates 650 and 660, which are in planarcontact with the opposed surfaces of the two heating plates 6220 and6230, face the outer surfaces of the hollow plate 610. Further, thesurface 653 of the upper metal plate 650 faces the hollow plate 610, andthe metal protrusion 654 of the surface 653 faces the hollow plate 610.

After placing the hollow plate 610 between the two heating plates 6220and 6230, as shown in FIG. 12F, the two heating plates 6220 and 6230 aremoved toward each other. This moves the heating plates 6220 and 6230toward the hollow plate 610 and brings the heated metal plates 650 and660, which are supported by respective heating plates 6220 and 6230,into planar contact with the outer surfaces of the hollow plate 610.Here, the metal plates 650 and 660, which are heated to a hightemperature, are bonded to the outer surfaces of the hollow plate 610through thermal fusion caused by their own heat.

The metal protrusion 654 in the surface 653 of the upper metal plate 650presses the surface of the hollow plate 610 that faces the upper metalplate 650. The metal protrusion 654 of the upper metal plate 650 isheated to a high temperature as with the upper metal plate 650. Thus,cells S in the hollow plate 610 are compressed and deformed by thepressing force from the metal protrusion 654. In addition, the hollowplate 610, which is made of a thermoplastic resin, is heated and meltedto form a plastic recess 611, and the metal protrusion 654 (metal recess651) of the upper metal plate 650 is bonded to the outer surfacedefining the plastic recess 611 by thermal fusion. This forms a recess670 in the lamination structure.

After the metal plates 650 and 660 are brought into planar contact withthe outer surfaces of the hollow plate 610, the air suction through theheating plates 6220 and 6230 is stopped, and the heating plates 6220 and6230 are moved away from each other. In this process, the heating plates6220 and 6230 sandwich the hollow plate 610 through the metal plates 650and 660 only for a very short time. Thus, the heat of the heating plates6220 and 6230 is not transferred excessively to the hollow plate 610.This limits excessive softening of the core layer 620 of the hollowplate 610, thereby limiting strength reduction of the hollow plate 610.

After bonding the metal plates 650 and 660 to the outer surfaces of thehollow plate 610 by thermal fusion, as shown in FIG. 12G, the hollowplate 610, which is placed between the two heating plates 6220 and 6230,is moved to be placed between two press plates 6240. The plane shape ofthe press plates 6240 is larger than or equal to the plane shape of themetal plates 650 and 660. In FIGS. 12A to 12I, the press plates 6240 andthe metal plates 650 and 660 are shown as the same size. Unlike the twoheating plates 6220 and 6230, the press plates 6240 are not heated andhave ordinary temperature. The press plate 6240 facing the upper metalplate 650 and the press plate 6240 facing the lower metal plate 660 areboth flat and free from a recess or protrusion.

As shown in FIG. 12H, after placing the hollow plate 610 between the twopress plates 6240, the press plates 6240 are moved toward each other.The two press plates 6240 sandwich and press the hollow plate 610 in thethickness direction with a predetermined pressure. The press plates 6240press the entire areas of the metal plates 650 and 660 against thehollow plate 610. The metal plates 650 and 660 are pressed against andbonded to the hollow plate 610 under uniform pressure. This adjusts thethickness of the lamination structure and forms a flat planar laminationstructure that is free from warpage. Then, the two press plates 6240 aremoved away from each other. As shown in FIG. 12I, the hollow plate 610to which the two metal plates 650 and 660 are bonded by thermal fusion,or the lamination structure including the recess 670, is then moved awayfrom between the two press plates 6240.

Operation of the third embodiment will now be described.

The upper metal plate 650 having the metal recess 651 (metal protrusion654) is preheated and then bonded to the hollow plate 610 by thermalfusion. Pressing the hollow plate 610 with the metal protrusion 654 ofthe heated upper metal plate 650 compresses and deforms the hollow plate610 with the pressing force from the metal protrusion 654. In addition,the metal protrusion 654 thermally melts the hollow plate 610, which ismade of a thermoplastic resin, by its own heat and forms the plasticrecess 611. Further, the metal recess 651 (metal protrusion 654) of theupper metal plate 650 is bonded to the hollow plate 610 to form therecess 670 of the lamination structure.

Instead of forming the metal recess 651 (metal protrusion 654) in theupper metal plate 650 in advance, a flat upper metal plate 650 could bebonded to the hollow plate 610. In this case, after forming thelamination structure, the lamination structure may be stamped bypressing the outer surface of the upper metal plate 650 with a recessedjig to form a recess in the surface of the lamination structure.However, in this method, the pressing force of the jig acts not only onthe upper metal plate 650 but also on the hollow plate 610. This hinderscontrolling of the depth of the recess 670. In addition, due to thelimited flexibility of the metal plate, the upper metal plate 650 maycrack when a deep recess 670 is formed. In this respect, the thirdembodiment forms in advance the metal recess 651 (metal protrusion 654)in both sides of the upper metal plate 650 by stamping, and the heatedupper metal plate 650 is bonded to the hollow plate 610 by thermalfusion. This avoids the problems described above. In addition, since theupper metal plate 650 that already has the metal recess 651 is used forthermal fusion, a recess 670 of 5 mm or more or even 10 mm or more maybe formed. Further, the recess 670 may be formed with a steep angle,such as a right angle, between the side walls 671 and the base wall 672of the recess 670. In other words, the recess 670 can be easily formedin a desired shape.

When the upper metal plate 650 is heated to a relatively hightemperature and pressed against the hollow plate 610 at reduced pressingspeed, cells S are pressed equally while the thermoplastic resin meltsin the section of the hollow plate 610 in which the plastic recess 611is being formed. In this case, as shown in FIG. 13A, the thermoplasticresin forming the hollow plate 610 melts and forms molten resin pools inthe cells S. At the same time, the distance between the upper walls 621and the lower walls 622 becomes narrower with the side walls 623 of thecells S remain standing between the upper walls 621 and the lower walls622. Consequently, the internal cavities of the cells S are narrowed,and solidified resin pools R are formed after the molten resin cools andhardens. This increases the strength of the thinner section. The term“solidified resin pool” in the appended claims refers to the state inwhich the thermoplastic resin forming the hollow plate 610 has meltedand then cooled and hardened. The solidified resin pool R increases thestrength of the recess 670 of the lamination structure.

When the upper metal plate 650 is heated to a lower temperature and thepressing speed of the upper metal plate 650 is increased, the section ofthe hollow plate 610 in which the plastic recess 611 is being formed iscompressed and deformed by the pressing force of the metal protrusion654 while a lower amount of thermoplastic resin melts. In this case, asshown in FIG. 13B, the side walls 623 of the cells S collapse in thesame direction between the upper walls 621 and the lower walls 622 whilethe distance between the upper walls 621 and the lower walls 622 becomesnarrower. Accordingly, the solidified resin pools R and the compressionof cells S, which is caused when the hollow plate 610 becomes thinner,improve the strength of the section under the recess 670 of thelamination structure.

Alternatively, the heating temperature and the pressing speed of theupper metal plate 650 may be adjusted such that the side walls 623 ofcells S collapse irregularly between the upper walls 621 and the lowerwalls 622 while the thermoplastic resin melts and forms resin pools inthe cells S as shown in FIG. 13C. The molten resin cools and hardens toform solidified resin pools R, thereby improving the strength of thesection where the thickness is reduced.

Adjusting the heating temperature and pressing speed of the upper metalplate 650 allows for modification of the state of cells S under theplastic recess 611 and adjustment of the strength of the section underthe recess 670 in the lamination structure. The conditions may be set inview of the efficiency in the manufacturing process of the laminationstructure and the properties required for the intended product.

(13) The hollow plate 610 of the lamination structure includes theplastic recess 611, which is thermally deformed by the metal recess 651(metal protrusion 654) of the upper metal plate 650. The metal recess651 of the upper metal plate 650 is bonded to the plastic recess 611. Agiven component may be coupled to the section of the laminationstructure to which the metal recess 651 is bonded. For example, a holderor hook may be coupled to the metal recess 651. This allows thelamination structure to be used as a vehicle cargo cover. That is,coupling a given component to the recess 670 of the lamination structureincreases the usability of the lamination structure.

To couple a given component to the lamination structure, the depth ofthe recess 670 may be set such that the component coupled to thelamination structure is received in the recess 670 without protrudingout of the surface of the lamination structure. Such a laminationstructure can be used as a vehicle part such as a luggage board that isless likely to damage the luggage placed on the luggage board. Thelamination structure thus has functions that are desirable for a vehiclepart.

(14) The heating plate 6220 for the upper metal plate 650 includes theprotrusion 6221 shaped to conform to the inner shape of the metal recess651 of the upper metal plate 650. The heat of the heating plate 6220 isthus easily transferred to the metal recess 651 of the upper metal plate650. This facilitates the compression deformation and thermal fusion ofthe hollow plate 610 by the metal protrusion 654 of the upper metalplate 650. In addition, the section of the heating plate 6220 other thanthe protrusion 6221 is brought into planar contact with the upper metalplate 650 and thus evenly heats the upper metal plate 650, allowing theupper metal plate 650 to be bonded uniformly to the outer surface of thehollow plate 610 by thermal fusion.

The third embodiment may be modified as follows.

The side walls 671 do not have to be at about right angle with respectto the plane including the base wall 672 and may be at 5° to 90°, 20° to90°, or 45° to 90°. A reduced angle between the side walls 671 and theplane including the base wall 672 forms the recess 670 in the surface ofthe lamination structure with less steepness. An increased angle betweenthe side walls 671 and the plane including the base wall 672 improvesthe bending strength of the section under the recess 670, therebyimproving the strength of the lamination structure. That is, the anglemay be set as appropriate depending on the function or usabilityrequired for the lamination structure.

At least one of the side walls 671 and the base wall 672 may be concave,convex, or curved to form an S-shaped cross section. In this case, theangle between the side walls 671 and the base wall 672 may be determinedby approximating the uneven surface to an even surface.

The upper metal plates 650 may be formed by a plurality of plates. Inthis case, the metal protrusion 654 may be formed of a plate thatdiffers from the plate forming the other section, and the other sectionmay be formed by a plurality of plates. The plates may differ inthickness, material, or the like. This may improve the bending strengthand reduce the weight of the lamination structure. The same applies tothe lower metal plate 660.

When bonding the metal plates 650 and 660 to the hollow plate 610, astep may be added to remove air the in hollow plate 610. Air can betrapped in the hollow plate 610 when bonding the superficial layers 630and 640 to the core layer 620. The air in the hollow plate 610 maycontract after the metal plates 650 and 660 are bonded, bending themetal plates 650 and 660 inward. When the metal plates 650 and 660 arebonded and the section under the plastic recess 611 becomes thinner, thecompressed air in the hollow plate 610 may bend the metal plates 650 and660 outward. Process of removing air lessens the likelihood of the metalplates 650 and 660 bending upward or downward.

One or both of the superficial layers 630 and 640 of the hollow plate610 may be omitted, and the metal plates 650 and 660 may be bonded tothe core layer 620 directly.

The thermoplastic resin that forms the hollow plate 610 may include aflame retardant resin, for example, to improve the flame redundancy.Further, talc or inorganic material may be added to increase thespecific gravity. All or at least one of the core layer 620 andsuperficial layers 630 and 640 may include various functional resins.

The surface of the lamination structure that includes the upper metalplate 650 has only one recess 670. However, there is no limitation tothe number of the recess 670, and a plurality of recesses 670 may beformed. A plurality of recesses 670 may be formed in both sides of thelamination structure, where the upper metal plate 650 and the lowermetal plate 660 are located. Further, a plurality of recesses 670 may beformed over the entire metal plates 650 and 660 such that one or both ofthe surfaces of the lamination structure is corrugated. In this case,upper and lower dies may be used that include recesses and protrusionsin the number corresponding to the number of recesses 670.Alternatively, a plurality of metal recesses may be formed by repeatingstamping multiple times using upper and lower dies each having a singlerecess or protrusion.

Prior to stamping the upper metal plate, the section corresponding tothe base wall of the metal recess may be stamped out, and the sectionscorresponding to the borders between the side walls may be cut to formslits. For example, as shown in FIGS. 14A and 14B, the rectangularsection of the upper metal plate 650 corresponding to the base wall 656of the metal recess 651 may be stamped out, and four cuts 657 may beformed in the borders between adjacent side walls 655 of the metalrecess 651 in advance.

When stamping such an upper metal plate 650, a line connecting the fourcuts 657 in the upper metal plate 650 (the dotted line in FIG. 14A) isaligned with the upper edge of the recess in the lower die, and theupper die is moved toward the lower die to stamp the upper metal plate650. When bonding the metal plates 650 and 660 by thermal fusion, theprotrusion 6221 of the heating plates 6220 or 6230 is pressed againstthe hollow plate 610. This forms the plastic recess 611 in the hollowplate 610 and thus a lamination structure including the recess 670.

Such preprocessing of the upper metal plate 650 facilitates deformationof the side walls 655 when stamping the upper metal plate 650 as shownin FIG. 14B. This limits cracking of the upper metal plate 650 even whena deep metal recess 651 is formed. The appearance of the recess 670 inthe lamination structure is thus improved.

The cuts 657 are not limited to slits and may be wider and trapezoidal.When stamping the upper metal plate 650, the rectangular sectioncorresponding to the base wall 672 and the cuts 657 may be stamped outsimultaneously. Further, the rectangular section and the cuts 657 may beformed simultaneously with the side walls 655 of the metal recess 651.

As shown in FIG. 15A, a recess 770 may include an base wall 772 thatincludes a hole 773 extending through a lower metal plate 760. That is,a metal recess 751 of an upper metal plate 750 may include a hole, and aplastic recess 711 of a hollow plate 710 may include a hole. In thiscase, a component such as a holder or hook may be coupled to sandwichthe base wall 772 of the recess 770. The metal plates 750 and 760 arebonded to the upper and lower sides of the base wall 772. This ensuresthe coupling of the component into the hole 773 even when the overlapallowance between the component and the base wall 772 is limited.

As shown in FIG. 15B, a recess 770 may be formed in the upper side ofthe lamination structure, where the upper metal plate 750 is located,and another recess 770 may be formed in the same position in the lowerside, where the lower metal plate 760 is located. The recess 770 in theupper side may be identical to or different from the recess 770 in thelower side in size and shape. Further, as shown in FIG. 15A, a hole 773may extend through both recesses 770.

As shown in FIG. 15C, a recess 770 may be formed in an end section ofthe lamination structure. In this case, a component such as holder orhook may be coupled to the end section of the lamination structure. Sucha lamination structure may be used as a vehicle part such as a vehiclecargo cover that is opened and closed by pulling the end section.Further, as shown in FIG. 15A, the base wall 772 of the recess 770 mayinclude a hole 773 extending through the lower metal plate 760. In FIG.15C, the recess 770 is formed in each of the upper and lower metalplates 750 and 760. However, the recess 770 may be formed only in one ofthe metal plates 750 and 760.

The recess 770 may have any shape, such as a circular shape or irregularshape as viewed from above. The base wall 772 of the recess 770 mayinclude an additional recess, and steps may be formed.

The recess 770 may be of any size, and the recess 770 may occupy most ofthe area of the upper metal plate 750. When the recess 770 occupies agreater area of the entire upper metal plate 750, the section other thanthe recess 770 is a projection of the upper metal plate 750. The sectionthat is thermally deformed by the upper metal plate 750 and locatedlower than the projection forms the recess 770.

As shown in FIG. 15D, the upper metal plate 750 may be bonded only tothe upper surface of the hollow plate 710 by thermal fusion. In thiscase, the side of the lamination structure where the upper metal plate750 is bonded to the hollow plate 710 includes a recess 770 that isformed by the pressing force of the metal protrusion 754 (metal recess751) and thermal fusion. On the side of the hollow plate 710 that isopposite to the upper metal plate 750, the section corresponding to therecess 770 bulges. In this case, the upper metal plate 750 and theplastic recess 711, where the hollow plate 710 is thermally deformed andthinner, improve the strength of the hollow plate 710. The usability ofthe lamination structure may be increased by coupling a component suchas a holder or a hook to the recess 770. When bonding the upper metalplate 750, a support member may be positioned on the side of the hollowplate 710 opposite to the upper metal plate 750 to limit partial bulgingof the hollow plate 710.

As shown in FIGS. 16A and 16B, metal plate 850 and 860 may be bonded toboth sides of a hollow plate 810 excluding sections in one end. A metallooped holder 890, which is heated, may be moved sideways to the hollowplate 810 to heat and compress the hollow plate 810. This couples theholder 890 to the hollow plate 810. In this case, the holder 890corresponds to the “metal component” in the appended claims, and theheated and compressed side section of the hollow plate 810 correspondsto the “plastic recess” in the appended claims.

Alternatively, a metal plate 850 or 860 from which a section is removedmay be bonded to the upper or lower side of the hollow plate 810, and ametal component may be bonded to the section of the hollow plate 810 towhich the metal plate 850 or 860 is not bonded. For example, as shown inFIG. 16C, an upper metal plate 850 from which a section is removed maybe bonded to the upper surface of the hollow plate 810, and a metallooped holder 890, which is heated, may be bonded to the section of thehollow plate 810 to which the upper metal plate 850 is not bonded. Asshown in FIG. 16D, the bonded holder 890 protrudes outward from theupper metal plate 850 of the hollow plate 810.

We claim:
 1. A lamination structure in which a metal plate is bonded toa hollow plate that is made of a thermoplastic resin and includes aplurality of cells formed inside the hollow plate, wherein the metalplate includes an edge located inward of an edge of the hollow plate ina plane direction of the lamination structure.
 2. The laminationstructure according to claim 1, wherein the hollow plate has an edgesection that is located outward of the edge of the metal plate andincludes an inclined surface inclined toward middle in a thicknessdirection of the hollow plate.
 3. The lamination structure according toclaim 2, wherein the hollow plate includes a flat surface extendingbetween the edge of the metal plate and the inclined surface in theplane direction of the lamination structure, and a width of the flatsurface between the edge of the metal plate and the inclined surface isequal to or less than a thickness of the lamination structure.
 4. Thelamination structure according to claim 1, wherein the hollow plateincludes a sealing section located outward of the edge of the metalplate, and the sealing section is formed integrally with the hollowplate from the thermoplastic resin forming the hollow plate and sealsthe hollow plate so that internal cavities of the cells are not exposedto outside of the hollow plate.
 5. The lamination structure according toclaim 1, wherein the sealing section includes an inner edge sectioncovering the edge of the metal plate.
 6. The lamination structureaccording to claim 4, wherein the sealing section is formed bycompressing a periphery of the hollow plate inward in a plane directionof the hollow plate.